This invention relates to the steering of vehicles, such as cotton harvesters, having forward main drive wheels and a rear steerable guide wheel controlled by a hydrostatic steering system and, more particularly, to apparatus therefor for indicating to the operator the guide wheel position relative to the direction of travel.
In a cotton harvester, especially one having a single rear steerable guide wheel, the operator is mounted forwardly above the main drive wheels to observe the harvesting operation and guide the harvester. In normal conditions, as the main drive wheels pull the harvester down the row, the steerable guide wheel adjusts and controls the direction of the harvester. However, in muddy, slick field conditions, the steerable rear wheel may skid and not steer the harvester, leaving the operator to use his individual brakes on the main wheels to maintain the direction of the harvester. With the conventional hydrostatic steering, the wheel may become turned out of fore-and-aft alignment without the operator even being aware of it. Besides causing greater power consumption, an off center position of a skidding wheel could also cauuse an unexpected turn should the wheel encounter dry ground. Another problem is that cotton harvesters are provided with side dumping baskets and when they are pulled alongside a trailer to dump the basket, the steerable guide wheel may become turned, so that upon pulling away from the trailer, the rear end of the harvester swings into the trailer causing damage.
Others have provided various devices for mechanically indicating the position of the steerable wheels in automobiles based on the position of the steering wheel. See, for example, U.S. Pat. Nos. 2,934,035 to Hardy and 3,103,909 to Anderson. Coon U.S. Pat. No. 2,957,442 additionally illustrates an electrical system for doing the same. These systems measure the position of the steering wheel shaft and are not applicable to vehicles such as cotton harvesters having hydrostatic steering systems wherein there is no mechanical connection between the steering wheel shaft and the steerable guide wheel. Still others have provided a cotton picker with an electrical circuit to indicate whether the guide wheel is in fore-and-aft alignment with the line of travel. The latter system does not indicate the direction is which the steerable guide wheel will steer the cotton harvester. Moreover, the electrical circuit thereof includes a push button switch externally mounted to the frame adjacent the guide wheel assembly, the switch being mechanically actuated by a cam means mounted on the guide wheel. The external environment of a cotton harvester often includes cold, wet, and muddy conditions as well as a considerable amount of vibration and high amplitude movement caused by the cotton harvester encountering the extreme variations in the ground surface present in agricultural fields. Besides the additional costs, an external switch would be less reliable under these conditions.